1. Field of the Invention
The present invention relates to a base station, a mobile station and a radio network controller which support multicast communication.
2. Description of the Related Art
As shown in FIG. 1, broadcast communication whereby a plurality of base stations 11 to 17 transmit common information to unspecified mobile stations 101 to 112 in predetermined areas is known in a conventional radio communication system.
As shown in FIG. 2, multicast communication whereby a plurality of base stations 1 to 17 transmit common information to specific mobile stations joining in (belonging to) a specific group is known in a conventional radio communication system.
However, there is a problem in that a plurality of mobile stations joining in a multicast group receive a controls signal for the multicast group at approximately the same time, and a plurality of response signals are transmitted to the radio network controller at approximately the same time, so that the load on receiving controlling and processing of the radio network controller is increased as the number of response signals increases in the conventional multicast communication.